A plurality of series circuits each consisting of a current-carrying element and an element to be measured are provided between a power supply potential VDD and a ground potential VSS. The current-carrying elements are supplied with a test signal commonly, and corresponding selection signals, respectively. After a mode is set so that power consumption of a main circuit unit included in a semiconductor device is substantially zero or almost constant, the elements to be measured are energized sequentially and, in this state, a power supply current that flows through the semiconductor device is measured sequentially. Accordingly, it is possible to accurately know the power consumption of the element to be measured and it is also possible to know the characteristics of the element to be measured based thereon.